Water at 70°f flows by gravity from a reservoir at high elevation to a lower reservoir through a 60 ft length of pipeline made of 2 in cast iron. the pipeline includes a well-rounded entrance, 4 standard flanged elbows, a fully-open gate valve, and a sharp exit. to maintain a flow of 10 ft3/min, calculate the height of the free surface of the upper reservoir in ft relative to the free surface of the lower reservoir.